Vacuum-tube-filament connection and method of connecting



Sept. 2, 1930. cg H. BRAsELToN VACUUI TUBE FILAl-ENT CONNECTION AND METHOD OF CONNECTING Filed Jan. 25. 1928 R O T N E V m Patented 2, 1936 UNITED STATES PATENT OFFICE cnEs'rEE n. nnAsEL'r-ON, or NEw You, N.- Y., AssIeNon r.ro AEc'rUEUs RADIO TUBE oonrANY,.or NEWARK, NEW JEasEr, A OOEPOEATION or DELAWARE vAcU-Ux-TUEE-EMENT CONNECTION AND METHOD OrcONNEc'rINe Application med Ianuary, 1928. Serial No. 249,261.

This invention relates to vacuum tubes and more particularl to a method of connecting the ends of t e filaments commonly used in such tubes.

5 One of the objects ofthe invention is to provide a connection between a filament and the support therefor which will not be injuriously affected by the heat of the filament.,

Another object of the invention is to pro- 10 vide a method of connecting the ends of ,filaments to supports whereby the connection is protected from the excessive heat of 'the filament.

Another object of the invention is to pro- 15 vide means to conduct heat rapidly away from the ends of the filament. l

Another ob'ect of theinvention is to provide a metho of reinforcing the ends ofa ilament adjacent the supports therefor. zo 'Another object of the invention is to provide a means to increase the conductivity of the ends of the filament to reduce. the heatlin effect of the current therein. Vther objects Of the invention will be ap- 2 5 parent as the descri tion proceeds.

One embodiment o the invention has been illustrated in theaccompanying drawing in which:

, Fig. 1 is an elevation of a vacuumv tube 3o embodying my invention; and

Fig. 2 "s an enlarged view of the filament showing the means to connect it at each end of the support. 4

Referrin now more articularl' to the drawi t e invention as been s own in connection with a vacuum tube of theheater type such as is shown and described in the copending application of Walter L.- Krahl vacuum tube construction and circuit therefor S. N. 156,947 filed December 24, 1926. This vacuum., tube comprises an envelope 10 mounted on the usual base .(not shown) which carries the necessary terminals for connecting the vacuum tube to the circuit of the radio set. j A press 11 is provided within the envelo e into which the various supports for the e ements are sealed. A tubu arplate 12 is supported on'conductor rods .'(not shown) and ay cylindrical grid 13l is tn unounted inside of the plate', 12 in a manner well known i'n the art. Avtubu'l'ar electronemitting cathode 14 is also mounted within of a spring wlre 17 to the upperend of a support 18 which also formsl the 'support for the upper end of the cathode 14. A

Considerable difliculty lras been experienced in connecting thelends of the filament 15 to thelrsup Orts. In some instances metal tabs have een used which have been attached vto the filament and in turn welded to the sup Orts, but some objection has been found to t is method of attaching the ends,

inasmuchas it is difficult to attach the tabs to the carbon of the filament without damagin. the ends of the filament and causing Ossi le failure after a short use of the tube. n the present invention I have found that bg' copper plating the ends of the carbon t eylmay be welded directly to a support, which results in a simpler and more secure connection. This -is true es ecially of the lower end of thefilament w ich is welded to a nickel support 16. The u per end of the filamenthowever, is prefera 1y attached to the spring 17 whlch may be made of phosphor bronze,v for instance, or any 'other spring wire which cannot readil be welded to copper, and it is desirable, t erefore, in securlng the upper end of the filament, to nickel plate the end afterthe same hasbeen copper plated and then 'weld the nickel plated end dir'ectly tothe spring wire.

\ With the filament connected as indicated at its-lower and upper ends there is some danger of the plating fusing, due to .the high heat ,of the filament, which fusing mayV re,

sult' in l the evolutionof gases or a general Aweakening of the connection, either of whichV mi ht be detrimental tothe operation of the tu I have therefore found that if the juncture ofthe carbon with 'the plating on the filament is covered with a metallic paste, the paste-not only acts as a reinforcing agent to strengthen the ends of the lilament, and provides a means to rapidly conroo 2 atrasos duct heat away from the ends of the filament as well as to protect the ends from the radiant heat of the filament and cathode which prevents any danger of the fusing of the plating thereon, but also increases the conductivity of the ends and lowers the temerature thereof which would otherwise be igh due to the current flowing therethrough.

The construction is illustrated in Fig. 2 in which the filament l5 is plated with copper 19 at both ends and has a further plating of nickel 20 at its upper end. The metallic paste 2l is shown surrounding the filament at the point where the plating begins.

Such a metallic paste is well known in the art and may consist of Dixons graphite, caramel, gum arabic, cryolite, boracic acid, and silver nitrate. The paste is spread in a plastic state on 4the lament after the ends have plated and then allowed to dry which takes approximately one half hour, or, it

may dry in a shorter time if the temperature is increased.

This means of Connecting the upper and lower end of the filament, as is evident from the above description, is simple and very effective, and while I have shown and described one embodiment of the invention, it is evident that variations may be made in the manner of making the connection and in the type of metal and composition of the paste used without departing from the spirit of the invention, and I do not, therefore, desire to limit myself to the specific means and method shown and described, but to interpret the invention broadly within the scope of the ap pended claims.

What I claim is:

l. The method of attaching a carbon filament to a support which comprises plating the end of the filament, applyin a heat conducting paste to the plated en and welding said end to a support.

2. The method of attaching a carbon filament to a support which comprises plating the end of the filament, applying a reinforcing paste to the plated end and welding the plated end to a support.

3. The method of connecting a carbon filament to a support which comprises plating the end of the filament, covering a portion of the plated end with a metallic heatl conducting paste and welding the end of the filament to a support.

4. The method of welding a carbon filament to a support which comprises copper plating the end of the filament, covering a portion of the said end with heat conducting paste, and welding said end to a support.

5. The method of attaching a carbon filament to a spring support which comprises copper plating the end of the filament, nickel plating said end over the copper plate, covern ing a portion of said and with a coating of heat conducting paste, and Welding said end to a spring support.

6. The method of attachin a carbon filament to a spring support w ich comprises copper plating the end of said filament, nickel plating said end over the copper plate, covering a portion of said end with a coating of metallic paste, whereby said end is reinforced and welding said end to the spring support. v

7. In a. vacuum tube a carbon filament, a metallic plating on the end of said filament and a coating of heat conducting material on the filament at the juncture of the filament and plating.

8. In a vacuum tube a carbon filament, a metallic plating on the end of said filament and a coating of electrical conducting material on said filament at the juncture of the filament and plating.

9. In a vacuum tube a carbon filament, a metallic plating on the end of said filament, and a reinforcing material at the uncturc of the filament and the platino to protect the plating from the excessive heat of the filament.

l0. In a vacuum tube, a filament of high resistance material, a metallic plating on the end of said filament and a coatingr of metallic paste over the juncture of said filament and plating to protect said plating from the heat of said filament.

In testimony whereof, I affix m signature.

CHESTER H. BRA ELTON. 

